Blocking test fixture



Dec. 15, 1970 A'SDMOND 5 3,546,937

BLOCKING TESTFIXTURE Filed March-27, 1969 SOKOLSKI 8 WOHLGEMUTH ATTORNEYS United States Patent O 3,546,937 BLOCKING TEST FIXTURE Arthur S. Diamond, Palos Verdes Peninsula, Calif., assignor to Diamond Research Corporation, a corporation of California Filed Mar. 27, 1969, Ser. No. 811,062 Int. Cl. G01n 19/04 US. Cl. 73-159 5 Claims ABSTRACT OF THE DISCLOSURE An elongated hollow rectangular housing closed at one end and open at the opposite end is used for measuring the blocking resistance of sheet materials. Contiguous sheets of the materials are placed between divider plates and slidably fitted within the housing The divider plates and sheets rest on the closed end of the housing and then a plurality of weights are slidably fitted within the housing and rest on the plates. Slots are formed in the walls of the housing to extend from the closed end to the open end so the divider plates and weights can be readily slidably removed from the housing.

these materials are often further packaged in large stacks a of individual sheets. In both instances, of course, extreme pressure is exerted on adjacent sheets due to the overall weight of material. Often Whole large rolls of paper and the like have been completely lost and required destruction due to adjacent layers in the roll permanently sticking together. In apparatus such as duplicating machines and the like, where individual sheets are to be fed from a stack, any sticking of adjacent sheets in the storage portion of the device would obviously deleteriously affect the operation of the machine. Because of the foregoing, it becomes quite important to perform what is known as a blocking resistance test on these sheet materials.

The test has been somewhat standardized by TAPPI which stands for the Technical Association of the Pulp and Paper Industry. Blocking is defined as that degree of cohesion or adhesion between contiguous layers of similar or dissimilar packaging materials in rolled or sheet form which prevents their being satisfactorily of efiiciently used. Alternatively, the ability of given materials to resist the blocking effects of temperature, pressure and relative humidity, is considered as a significant attribute of that material and is designated as blocking resistance. The basic test set forth by TAPPI to determine blocking resistance of materials provides a range of standard conditions of temperature, relative humidity and constant pressure for given times. Thus, the test attempts to duplicate varying climatic conditions which can be encountered in the manufacture, storage, transportation and use of packaging materials.

Prior to the herein invention, the constant pressure required normally comprised placing the weights on top of the paper While the glass plate or a suitable metal plate would support the sheets. This apparatus is obviously quite clumsy, and could not be readily transported in toto. Furthermore, when a glass plate was used, or heavy glass plates which served as weights were sometimes used, they were obviously subject to breakage. A further disadvantage of the apparatus was that it was far from being standardized and thus one would have to improvise as best as possible the suitable combination of materials to perform the standardized test. Further, the apparatus has to be transferred into a dessicator and then into an oven and out again, which is not readily achievable with the many separated elements required.

Thus, an object of this invention is to provide a compact simple device for performing a blocking resistance test of paper and other flexible materials.

Still another object of this invention is to provide a device for readily testing the blocking resistance of paper and flexible materials which is easily transportable as an entire unit.

The above and other objects of this invention are accomplished by a device that is comprised of a rectangular elongated housing closed at one end with a solid base. Opposite walls of the housing have slots formed therein running the entire length of the housing. A plurality of thin divider plates are insertable in the housing adjacent the base portion. On top of the divider plates are then disposed a plurality of weight plates. The divider plates and weight plates have the same dimensions and configuration which correspond to that of the housing so that they are slidable within the housing. When the divider plates and weights are inserted within the housing,

they completely occupy the wall space therein. The base of the housing is preferably provided with a notched area adjacent each elongated slot in the wall portion so that one can grip the bottom plates in attempting to slidably remove them from the device. Further, the apparatus is provided with a rotatable handle that is connected to the housing and allows the device to be easily transported. It is believed the invention will be better understood from the following detailed description and drawing, in which:

The figure represents an expanded pictorial representation of the device of the invention including its divider plates and weights, further disclosing the location of paper sheets between the divider plates.

Turning now to the figure, there is seen the device of this invention which comprises a housing 11 of generally rectangular configuration. Housing 11 is preferably constructed of a heavy duty material such as stainless steel which will not be easily dented or misshapen. Affixed to one end of housing 11 is a heavy base 13 which can be secured to the housing by screws 15 or the like. Two slot areas 17 are provided in opposite walls of the housing 11, and extend from the open top portion 19 to the base 13. As can be seen in the particular construction shown, the housing 11 is really comprised of two separate elements that are secured to the base 13 and inherently provide for the slot areas 17.

The apparatus of this invention is further provided with a. plurality of thin separator plates 21, with five shown by way of example. However, any desirable number can be utilized. The separator plates 21 can be made of thin stainless steel or the like and serve to separate sheets of paper or other material 23 to be tested in the device in a manner to be further explained. The divider plates 21 together with the paper or sheets 23 therebetween are first inserted into the housing 11 to be disposed adjacent base portion 13. The dimensions of the plates 21 are such that they conform to the dimensions of the housing 11 yet are readily slidable therein. On top of the divider plates 21 together With the material being tested 23, are placed a series of weights 25, preferably four in number. By having a plurality of weights one can thus control the amount of pressure per square inch placed on the material 23 being tested. In the calculations, the thin divider plates 21 are assumed to contribute very little weight per square inch and thus the Weight is figured based upon the elements 25. When the weights are all inserted within the housing 11, they fully occupy yet do not extend beyond the top surface 19.

The device is provided with a rotatable handle 27 which can rotate from an upright position as shown to a horizontal one due to a stop 29 formed on a bushing 31 on which the handle is pivotally mounted. In the view, only one such bushing is shown while obviously two are utilized, one on each side of the device. In its upright position, the handle 21 provides a distance X between the handle and the top 19 of the housing 11 to allow at least one weight to pass therebetween. In order to lift all the weights and separator plates en masse from the device, the handle must be rotated so that it does not block the top 19.

It has been found that it is often difiicult to grip the thin metal plates and paper therebetween to remove them from the housing 11 by placing ones hands or fingers through the slot at opening 17. Thus, it is preferred that the base 13 is cut out or milled at 37 surrounding the slots 17 on each side. Thus the plates 21 will tend to overlap and be exposed at the portion 37 allowing one to place the hand or fingers underneath the plates 21 and lift them vertically upward through the slots 17.

In its forward or lowered position the carrying handle is held perpendicular to the vertical wall of the test device by means of a stop 29 in the bushing. Resting in this position the fiat, outside surface 33 of the handle is closest to the operator and provides a convenient location for labelling.

The need to label or identify one entire test unit develops when a number of such units are placed in the same oven or environmental chamber. Having the smooth, lateral face of the handle presented to the operator thus makes it easy to label and identify each unit.

In the upright or raised position a vertical stop 35 prevents the handle from swinging rearward. This stop prevents the test device from swinging back and forth when it is carried by the operator from place to place. The rear stop 35 does not prevent swinging entirely but does restrict the motion of the device. Without this restriction the tester could tilt to an extreme position while being carried by its handle and such tilting might cause one or more of the weights or separator plates to shift position. Thus it can be seen that the stops 29 and 35 limit the rotation of the handle 27 to approximately 90 degrees.

In the device of the herein invention, typical dimensions of the plates 21 and weights 25 can be 3 x 3 inches for a total surface of 9 square inches. Each weight, for example, could thus weigh 2.25 lbs., for a total weight of 9 lbs., such that when all the weights are in the device a pressure of 1 pound per square inch is placed upon the paper or other material 23 between the plates 21. Thus, with only two weights present, a pressure of 0.5 pounds per square inch is placed upon the test specimens. Thus, with this size apparatus the test specimens 23 are cut to 3 x 3 inch squares. Between each separator plate 21 the specimens are generally laid as follows: One specimen face up, one specimen face down, thus presenting a face to face arrangement between these two specimens. The next specimen is laid face down so that it has a face to back relationship with the adjacent one. Finally, one specimen is laid face up so it is in a back to back relationship with its adjacent specimen. On top of this is placed a separator plate 21. The same arrangement is then repeated as many times as desired between the number of separator plates utilized. The separator plates with the specimens are then placed in the housing 11 together with the desired weights. For example, in the standard TAPPI test, a weight of 0.5 pounds per square inch is utilized, thus only 2 of the herein weights 25 would be used. However, often it is desirable to test the specimens under increased weight conditions, and thus the additional weights are available. The simple device is then placed in a constant temperature oven which can be maintained at temperatures between to 150 F. for at least one hour. After this, the device is removed and placed in the desiccator which is used as a humidity chamber. As pointed out in the TAPPI test literature, the humidity conditions are obtained by utilizing sodium chloride to achieve a 75% relative humidity and a potassium carbonate solution to obtain a 44% relative humidity, depending upon the temperatures of the desiccator. The desiccator contining one of the aforegoing salt solutions is then placed in an oven wherein the temperature can be controlled to the desired level. The desiccator and apparatus therein is then left in the oven for about 24 hours. After this, the desiccator is removed and the apparatus is allowed to return to ambient conditions for one half hour before examination. The specimens are inspected. If there is no adhesion between their surfaces, there is no blocking. Slight blocking entails a very slight adhesion such that the adjacent surfaces do not slide freely but with frictional pressure. Considerable blocking exists when there is adhesion or cohesion of contiguous surfaces. Layers are separated only with difiiculty under this condition. Complete blocking exists when there is a seal or weld between adjacent surfaces which cannot be separated without destruction of the test specimen.

I claim.

1. A device for measuring the blocking resistance of sheet materials comprising:

an elongated hollow rectangular housing closed at one end thereof and open at the opposite end,

a plurality of thin divider plates slidably fitted within said housing,

a plurality of weights slidably fitted within said housslots formed in the walls of said housing extending from said closed end to said open end thereof whereby said divider plates and said weights can be readily slidably removed from said housing.

2. The device of claim 1 further comprising:

a rotatable handle attached to opposite sides of said housing adjacent the open end thereof.

3. The device of claim 2 wherein said handle is rotatable about from a vertical upright position to a horizontal one.

4. The device of claim 2 further comprising:

said slots formed in the two walls opposite said walls to which said handle is afiixed.

5. The device of claim 3 further comprising:

indentations formed in the base of said device adjacent said slots whereby said plates and said weights can be gripped to slidably remove them from said device.

References Cited UNITED STATES PATENTS 2,406,989 9/1946 Bonner et al. 73-150 2,469,013 5/1949 Sobota 73159 3,323,359 6/1967 Ely et al. 73150 LOUIS R. PRINCE, Primary Examiner H. C. POST III, Assistant Examiner US. Cl. X.R. 73-l50 

